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A cancer diagnosis often comes from out of nowhere. And it is a life-altering experience. Researchers around the world are working on ways to fight cancer in a more targeted way. As part of these efforts, Bayer’s scientists have developed a substance that works through alpha radiation to treat patients with prostate cancer, the second most common form of this disease in men worldwide. Siegfried Stark has benefited from this approach.

Many things become more valuable as time goes by. Siegfried Stark’s green racing bike is one of those things. It’s
a real collector’s item. The retired bricklayer used to ride 3,000 kilometers a year on it, over hill and dale.
It’s just one of ten bicycles stored in the cellar of his home in Gieboldehausen near Göttingen, Germany.
But the most precious thing – at least for him – is that he associates many memories with his bicycle.

Today the 77-year-old is very happy that he can ride his bike again. That’s because three-and-a-half years ago, he
was diagnosed with prostate cancer. The majority of newly diagnosed cases of prostate cancer are diagnosed in men aged
above 70. In the case of Stark, the cancer had already spread, or metastasized, to his pelvic bones. “I was shocked
when I got the diagnosis. I couldn’t believe it. I’ve always tried to lead a healthy life,” says Stark.
He underwent a routine cancer checkup every year after he turned 50. “When the diagnosis came, I had so many thoughts
going through my head. All of a sudden death, was a possibility. That wasn’t easy for me and my family.”
Especially considering it wasn’t the first time that Stark had had to deal with the issue of cancer: His daughter
Manuela was diagnosed with lymphoma back when she was at school – and then with breast cancer in her mid-30s. She
underwent chemotherapy and an operation. Today, the 48-year-old administrative specialist lives with her husband and
two children not far from her parents. “My daughter survived cancer twice. That gave me hope,” says Stark.

The retired bricklayer does what he can to keep his house in good condition, such as painting the window frames.
The garden provides all the fruit and vegetables that Siegfried Stark and his wife need.

A father of three and a grandfather of two, Stark initially received hormone suppression therapy in order to suppress the
growth of the cancer. After that, the retiree underwent six cycles of chemotherapy, but tolerated it poorly. “I
suffered from side effects and severe pain,” he recalls. His PSA level, which plays a role in cancer diagnosis
and monitoring, initially declined before climbing again after his final round of chemotherapy. For the active family
man, who had worked physically hard all his life, the illness resulted in constant ups and downs – until he was
treated at Göttingen University Hospital with a therapy that uses alpha radiation to fight bone metastases while
minimizing damage to the surrounding tissue.

It would be nice if I could stay active for another few years.

Siegfried Stark

Siegfried Stark spends as much time as he can with his family. Here he is pictured with his granddaughter Vanessa
and his wife Marlies in the garden.

Cancer patient Stark cycling with his grandson Adrian and having lunch with his daughter Manuela.

The alpha radiation emitted by radium-223 leads to double-stranded DNA breaks which the cancer cells cannot repair, eventually
leading to cell death. In Stark’s case, additional nuclear medicine imaging techniques known as bone scans revealed
that the known bone metastases had regressed and no new metastases had formed.

“The chemical structure of radium is similar to that of calcium, so it accumulates in the body wherever bone metabolism
is particularly active – for example in bone areas where there is uncontrolled growth of cancer cells, as is the
case with bone metastases,” explains Scott Fields, head of Oncology Development at the Pharmaceuticals Division.
This approach has been proven to be effective in advanced prostate cancer, which often metastasizes to the bones. On
the basis of the clinical results from a major Phase III trial with more than 900 patients, the compound has been approved
in more than 50 countries worldwide. Bayer scientists are now working on utilizing this technology to treat other types
of cancer. For this they are investigating thorium-227 in initial clinical studies. Thorium-227 also works by emitting
alpha particles that damage the DNA of cancer cells and which the cells cannot repair. In order to selectively reach
different types of tumors, the thorium is attached to a carrier molecule, for example a cancer-specific antibody, which
in turn binds to cancer cells. “This could enable us to fight other types of cancer as well, so we are going to
study this approach in several different tumor types,” says Fields.

Siegfried Stark from Gieboldehausen was able to fight back against his cancer, which stopped progressing after being treated
with the targeted alpha therapy – and now he can still enjoy growing fruit and vegetables in the garden with his
wife Marlies and keeping their house in good condition. He also continues to spend as much time as possible with his
children and grandchildren, and of course with his green racing bike. “It would be nice if I could stay active
for another few years,” Stark says.